4 spd hanging up... - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 04-09-2017, 04:55 PM Thread Starter
 
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4 spd hanging up...

Anyone have a problem with a 4 spd trans getting stuck in "no mans land" seemingly in both a forward and reverse gear at the same time? Shifter will not go into any gear and car will not move forward or back...is that just a shifter linkage adjustment?

Car is a 1969 with M20 or M21, stock hurst shifter and functioning reverse lock out in place.
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post #2 of 9 (permalink) Old 04-09-2017, 05:25 PM
 
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On first guess, sounds like linkage/shifter problem, not transmission. If the shifter is not aligned correctly by inserting the alignment pin in the alignment hole when it is in neutral, it may not be adjusted correctly and will not line up correctly when you go to shift. The shifter may be simply worn out and needs rebuilding or replacing. Are the linkage rods on correctly? Did you put both the shifter and the trans forks on the side cover in the "neutral" position when you installed/adjusted the rods? Are they the correct ones? The linkage bushings could be worn out and need replacing. Something could have gotten down into the shifter mechanism and is binding.

I would look to the shifter/linkages and even the mount to make sure nothing has loosened up or broke. If that all seems well, then look at the transmission as having an issue.
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post #3 of 9 (permalink) Old 04-14-2017, 07:59 PM Thread Starter
 
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Here is a question: if my clutch is out of adjustment, so that when I depress the pedal the clutch is still dragging the flywheel, could that cause the tans to hand up in between gears like this?
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post #4 of 9 (permalink) Old 04-15-2017, 08:07 AM
 
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Here is a question: if my clutch is out of adjustment, so that when I depress the pedal the clutch is still dragging the flywheel, could that cause the tans to hand up in between gears like this?
Yes, possible. The transmission is not being fully disengaged and it can feel like it is "locked-up" when you go to shift. You should also have difficulty getting the trans in gear when you first start out. If it is out of adjustment, you may find yourself grinding the trans into 1st gear. Your clutch pedal will most likely grab low at the floor (I like my clutch to grab at about half way up from the floor) which is another indication you need to adjust your clutch/linkage. Make sure your clutch pedal returns fully against the under-dash stop when you let up on the clutch pedal and does not just hang loose. Sometimes the return springs can break or be left off if anyone has been messing with the linkage/pedal.

Another thing could even be a broken engine/transmission mount allowing the engine/transmission to move around which can affect clutch/linkage adjustments which can show up under moderate/hard shifting as you torque over the engine.

Many things to check in diagnosing the problem. Could be worn out parts, something bent, trans shifter/linkages out of adjustment/worn, pilot bearing in the back of the flywheel worn out, clutch assembly going/gone bad, transmission bearings/synchronizers worn out, broken/missing teeth on transmission gears, etc.. Go with the simple stuff first, like check your engine/trans mounts, clutch adjustment, inspect for worn out clutch linkage parts, then check shifter/linkage adjustment. From that point on, it may require disassembly to inspect your clutch set-up and transmission.
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post #5 of 9 (permalink) Old 04-16-2017, 08:18 AM Thread Starter
 
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Whats happening here is that the trans is binding up, seemingly caught in both a forward and reverse gear (is that possible?) When I "clear" the jamn it shifts fine until coming out of reverse and going into a forward gear...usually comes out of reverse and goes 1, 2 and then jams going into third. When it happens the shifter is jammned and will not move into any gear...if you try to come off the clutch the car will not move but stall, as it seems, literally, to be in both forward and reverse, if that is possible. So when it happens the car can not be moved.

When it happens, I go under the car, detach 1-2 at the trans, position it in neutral and then go in the car and play around with shifter until it clears. Then it seems to shifts fine, 3-4 and into and out of reverse. Until I hook up 1-2. I immediately thought it was the 1 -2 adjustment but have adjusted it 3 times. I detached the reverse lock out as I thought maybe it was hindering the trans shifting in and out of reverse. Still does it.

I do think that the clutch adjustment is low. I am going to clear the trans, adjust the clutch pedal up and cross my fingers. If it still jams up is there anyway to diagnose this problem without throwing parts at the problem or removing the trans to inspect the clutch assembly?
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post #6 of 9 (permalink) Old 04-16-2017, 12:12 PM
 
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Originally Posted by gpm6367 View Post
Whats happening here is that the trans is binding up, seemingly caught in both a forward and reverse gear (is that possible?) When I "clear" the jamn it shifts fine until coming out of reverse and going into a forward gear...usually comes out of reverse and goes 1, 2 and then jams going into third. When it happens the shifter is jammned and will not move into any gear...if you try to come off the clutch the car will not move but stall, as it seems, literally, to be in both forward and reverse, if that is possible. So when it happens the car can not be moved.

When it happens, I go under the car, detach 1-2 at the trans, position it in neutral and then go in the car and play around with shifter until it clears. Then it seems to shifts fine, 3-4 and into and out of reverse. Until I hook up 1-2. I immediately thought it was the 1 -2 adjustment but have adjusted it 3 times. I detached the reverse lock out as I thought maybe it was hindering the trans shifting in and out of reverse. Still does it.

I do think that the clutch adjustment is low. I am going to clear the trans, adjust the clutch pedal up and cross my fingers. If it still jams up is there anyway to diagnose this problem without throwing parts at the problem or removing the trans to inspect the clutch assembly?

Well, I would adjust the clutch first because you may need that anyway. MY money is still on the shifter/linkage adjustments. Read this thread: Stuck in reverse!! Clutch in, car will not roll!!!! Muncie 4 spd | NastyZ28.com

To see if it's trans or linkage: By yourself put the shifter in neutral. Look under car at left side of tranny where linkages attach and see if both flat bars are straight up and down. If you have somebody else have them shift while you watch. Straight up and down is neutral. Reverse bar should be pointing forward. Only one flatbar should move at a time. To get the linkage right, disconnect it where the threaded portion is at the shifter then find neutral on the shifter and put a drill bit, allen wrench or whatever fits snuggly thru an alignment hole in the shifter gate that will lock the shifter linkages in neutral. Then adjust your linkage rods using the threaded end/nuts until each rod easily goes back on the flat bars attached to the transmission shift forks.

Found this: "Finally it shifts like a dream! My suggestion to anyone with this same problem is to grab another person to work the shifter while you're underneath. I was finally able to see that while it was aligned properly in neutral with the pin, the entire assembly was about 1/4 inch too far back. This made it hold onto second just enough to disrupt the shift into 3rd. By trial and error I kept shortening the linkage rod lengths by rotating the rod buttons with the helper rowing the gears till it hit the sweet spot."

You can tighten the shifter rods by using washers as spacers behind the clips that hold the rods to the shifter and the shift forks. Metal bushigs can also be used. The stronger you make the linkage, less slop the better it will feel. Make sure none of your holes are wallowed out or elongated.

I would try this first. Now I don't know much about the reverse lock-out rod assembly or how to adjust them - which may be part of the problem. It could still be a transmission problem - worn out bearings/bushings etc. and in need of some repairs -transmission parts do wear out, especially if I'm shifting on them. But start with the shifter/linkage adjustments and go from there.

Here is a diagram that you can use with instructions on making the adjustment: http://static.summitracing.com/globa...uu-3733163.pdf
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post #7 of 9 (permalink) Old 04-16-2017, 08:08 PM
 
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When you shift from 2nd to 3rd hold the shifter to the left until's in neutral THEN swing over to 3rd.It this helps your shifter is worn.
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post #8 of 9 (permalink) Old 04-20-2017, 09:08 AM Thread Starter
 
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Thank you to all as the information and links were very helpful. I readjusted the clutch pedal and 1-2 linkage and it is not binding up, although it is harder to get through the gate from 2 to 3.

Having done a little research, it appears that I have a "factory" Hurst 4 spd Comp Plus unit using aftermarket comp plus rods and levers. There is a difference, most noticeably in the method of adjusting the rods (factory employs a sleeve with locking nuts) and, most importantly for our conversation, the 1-2 lever, which is straight up and down on a stock unit and angled on an aftermarket. (the aftermarket 1-2 angle positions the lever toward the rear of car, like at 1pm on a clock, when aligned and not straight up and down) What I do not know is if the factory and aftermarket rods are also different in angles and/or length.

So, do I just get a factory (up and down) 1-2 lever and replace on the aftermarket rods or replace the rods and levers with factory units...its probably not a good idea to mix the factory and aftermarket rods and levers. If the stock rods vary from the aftermarket that could throw off the geometry as well, even with the correct levers...thoughts?
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post #9 of 9 (permalink) Old 04-20-2017, 06:14 PM
 
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Originally Posted by gpm6367 View Post
Thank you to all as the information and links were very helpful. I readjusted the clutch pedal and 1-2 linkage and it is not binding up, although it is harder to get through the gate from 2 to 3.

Having done a little research, it appears that I have a "factory" Hurst 4 spd Comp Plus unit using aftermarket comp plus rods and levers. There is a difference, most noticeably in the method of adjusting the rods (factory employs a sleeve with locking nuts) and, most importantly for our conversation, the 1-2 lever, which is straight up and down on a stock unit and angled on an aftermarket. (the aftermarket 1-2 angle positions the lever toward the rear of car, like at 1pm on a clock, when aligned and not straight up and down) What I do not know is if the factory and aftermarket rods are also different in angles and/or length.

So, do I just get a factory (up and down) 1-2 lever and replace on the aftermarket rods or replace the rods and levers with factory units...its probably not a good idea to mix the factory and aftermarket rods and levers. If the stock rods vary from the aftermarket that could throw off the geometry as well, even with the correct levers...thoughts?
OK, sounds like headway, anyway. I would not mix the levers - factory with aftermarket. This in my mind would throw off the geometry. Found this which has a picture of the linkages and a few more suggestions: Calling shifter Doctors, 4 speed hurst problems | NastyZ28.com
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